Place a frying pan over a low-medium heat. Heat the butter and add the shallots or onion, stirring constantly until soft and golden.
Add the sugar to the pan and stir over a low-medium heat for a couple of minutes.
Next, increase the heat, stir in the beer and bring to the boil. Reduce the heat and simmer, stirring occasionally, until the onions are golden brown and all the beer has evaporated.
Remove from the heat and stir in 1 tbs of Frank's RedHot® Original Cayenne Pepper Sauce, set aside.
Next, make the marinade by mixing the remaining Frank's RedHot® Original Cayenne Pepper Sauce, rosemary, olive oil and black pepper in a small bowl.
Rub the marinade all over the steaks.
Carefully lay the steaks on the BBQ or grill and cook for 2-3 minutes a side for medium-rare or 4–5 minutes for medium-well done. Once cooked, remove from the BBQ or grill and rest for 4 minutes before slicing thinly.
Top the bread with lettuce leaves, slices of steak, cheese and the beer caramelised onions and enjoy this mouth-watering sandwich in all it's glory!